u2 <-
function(x){
	nrm <- two_norm(x[-1])
	n <- length(x)
	if(nrm < 1e-12){
		c(0.5,0.5*rep(sqrt(1/(n-1)),n-1))
	}else{
		c(0.5, 0.5*(1/nrm)*x[-1])
	}
}

